help needed with 904

I think you're all set for parts now, but I've used Bulkpart.com or John Cope (Cope Racing Transmissions) for my transmission stuff for years now.
Some newbie hints - 5 cans of carb clean won't do it. Get a couple gallons of laquer thinner and a couple deep pans. One pan for "first cleaning", one pan for "final cleaning".
Shop air is your friend.
Get a couple brass bristle brushes to clean out the valve body.
Take one transmission apart at a time and don't confuse the snap rings or thrust washers.
Replace the tailshaft, 2nd gear drum, and pump bushings. If you can't do them all - do the tailshaft. All can be done without special tools.
Don't use a 5.0 lever on the kickdown band.
Do use vasoline or trans assembly grease - not white lube or heavier grease.
2 dental/seal picks really help assembling the clutch packs.
(too late for you) always check end play with a dial indicator before you start, and after you finish. It will "find" errors quickly.
Do not install the pump outer seal or sealing rings until final assembly.
Make sure the vent is clear when cleaning the pump.
Easiest way to assemble is the pump opening facing straight up.
Make sure the kickdown drum is fully engaging all the high gear clutch plates when you assemble. You can easily align the teeth using the two picks before you install the drum.
Pay attention to the kickdown band lever ratio (stamped into the side of it), and the appropriate band adjustment setting for the lever you are using.
Air test the trans before the valve body goes on.
Don't overtighten the valve body or trans pan bolts.